Firefox: If you pin and unpin "app tabs" in Firefox often, you're probably pretty annoyed by the constant right-clicking. With Easy App Tabs, all you need to do is double-click on a tab to pin it.

There isn't much else to say about this add-on—just install it and go. You don't even need to restart Firefox. After installing, you can pin and unpin tabs just by double-clicking on them, no context menu necessary.